It is related to a method of restoring a backup image, and in particular to a restore method for delta backup.
Generally, in information systems, data backup is performed for the quick recovery at the time of occurrence of faults. When a fault occurs in an information system, a user recovers the information system to its state before the fault occurrence by restoring a backup image at a specific point in time.
In particular, block-level delta backup is an effective way of backing up a large-capacity disk volume. In more detail, regarding such delta backup, a delta backup system is proposed which includes a storage device that is accessed in units of blocks having a predetermined size and stores data that is a target of backup, a latest update generation management mechanism that manages delta map information recording latest backup generations in which data in the respective blocks has been updated, and a delta management mechanism that receives data in each block in the storage system updated in a specified backup generation based on the delta map information and stores the data in the block, a position of the block in the storage system, and a backup generation, in which the block has been updated, in a backup device as a backup image. With this construction, it becomes possible to make backups in multiple generations only of each updated block on a disk, which increases the efficiency and reliability of backup work (refer to JP 09-101912 A).
Also, a technique is proposed with which at the time of backup of a shared disk, a cache control unit reflects data in a write cache of each computer in data on the shared disk, a copy management unit collectively copies data in multiple blocks of the shared disk to a backup medium, a block management unit and a group management unit list up each block that is a target of backup, and a log management unit saves a log of each computer on a log medium, thereby achieving efficient data backup (refer to JP 2001-290686 A).